Use of recombinant human deoxyribonuclease (DNase) for processing of a thawed umbilical cord blood transplant in a patient with relapsed acute lymphoblastic leukemia

This case report describes for the first time the use of a recombinant human enzyme deoxyribonuclease (rhDNase) containing solution for the processing of a thawed umbilical cord blood (UCB) unit prior to successful transplantation to avoid cell losses by clotting phenomena. A 6-year-old boy received an unrelated 2/6 HLA antigen mismatched UCB transplant for high-risk Burkitt type acute lymphoblastic leukemia. The UCB unit was provided as a volume-reduced sample after buffy coat separation with a final volume of 36 ml. To avoid the loss of nucleated cells due to cell clumping during thawing procedure cells were washed with a solution containing the rhDNase. No visible clotting of the resuspended unit occurred, and the patient was transplanted with 2.9x10(7) nucleated cells/kg body weight without any acute or chronic side effects due to rhDNase. On day +35, PCR analysis of bone marrow aspirate showed complete chimerism, and the child engrafted with an absolute neutrophil count greater than 0.5x10(9)/1 on day +47. Platelet transfusion independence was achieved on day +120. In conclusion, the supplementation of rhDNase to the washing and resuspension solutions of a thawed UCB unit is effective to prevent cell losses prior to transplantation. However, further investigations must be performed to confirm the safety of this procedure.